Microbial growth occurs in many systems in which aqueous media such as water, aqueous solutions and aqueous dispersions are employed.
For example, significant biofouling can occur in many areas of photoprocessing systems and, in particular, where low flow rate washes and water recycling is used. The problem may be overcome by adding biocides to the wash water tanks when bacterial biofilm formation becomes evident visually. However at this point the biocides may not work and even at quite high concentrations are not particularly effective because the bacteria have attached to surfaces to form colonies which have built up in layers. Hence, any biocide in solution can only reach the outer biofilm layer and not the inner layers of the biofilm which are protected. Furthermore, widespread use of such biocides is not desirable because they are relatively expensive and toxic chemicals which require specialised disposal to protect the environment.
It is known that in addition to being used up in the process of inhibiting the growth of microorganisms, biocides tend to degenerate and lose their activity through prolonged contact with the aqueous medium being treated.
EP-A-0 733 304 describes a biocidal material comprising a biocide immobilized on a support characterised in that the biocide has a log P value of at least 1.5, the support has a hydrophobic surface and the biocide is immobilized on the hydrophobic surface by hydrophobic exclusion. The support may take the form of polymer beads which may be held in a container having an inlet and an outlet so that the aqueous medium to be treated can be contacted with the beads by passing it through the container. An advantage of the material is that the biocide remains attached to the support. The material may be used to inhibit microbial growth in the wash water or other solutions used in a photoprocessor.